ジャーナル: Nature / 年: 2006 タイトル: A mechanical explanation of RNA pseudoknot function in programmed ribosomal frameshifting. 著者: Olivier Namy / Stephen J Moran / David I Stuart / Robert J C Gilbert / Ian Brierley / 要旨: The triplet-based genetic code requires that translating ribosomes maintain the reading frame of a messenger RNA faithfully to ensure correct protein synthesis. However, in programmed -1 ribosomal ...The triplet-based genetic code requires that translating ribosomes maintain the reading frame of a messenger RNA faithfully to ensure correct protein synthesis. However, in programmed -1 ribosomal frameshifting, a specific subversion of frame maintenance takes place, wherein the ribosome is forced to shift one nucleotide backwards into an overlapping reading frame and to translate an entirely new sequence of amino acids. This process is indispensable in the replication of numerous viral pathogens, including HIV and the coronavirus associated with severe acute respiratory syndrome, and is also exploited in the expression of several cellular genes. Frameshifting is promoted by an mRNA signal composed of two essential elements: a heptanucleotide 'slippery' sequence and an adjacent mRNA secondary structure, most often an mRNA pseudoknot. How these components operate together to manipulate the ribosome is unknown. Here we describe the observation of a ribosome-mRNA pseudoknot complex that is stalled in the process of -1 frameshifting. Cryoelectron microscopic imaging of purified mammalian 80S ribosomes from rabbit reticulocytes paused at a coronavirus pseudoknot reveals an intermediate of the frameshifting process. From this it can be seen how the pseudoknot interacts with the ribosome to block the mRNA entrance channel, compromising the translocation process and leading to a spring-like deformation of the P-site transfer RNA. In addition, we identify movements of the likely eukaryotic ribosomal helicase and confirm a direct interaction between the translocase eEF2 and the P-site tRNA. Together, the structural changes provide a mechanical explanation of how the pseudoknot manipulates the ribosome into a different reading frame.
名称: Rabbit reticuloyte ribosome stalled on IBV mRNA containing pseudoknot with tRNA and eEF2 タイプ: sample / ID: 1000 集合状態: One each of 40S, 60S, mRNA, eEF2 and P-site tRNA Number unique components: 5
The particles were selected in a semi-automated fashion using BOXER (EMAN suite)
CTF補正
詳細: By micrograph
最終 再構成
想定した対称性 - 点群: C1 (非対称) / アルゴリズム: OTHER / 解像度のタイプ: BY AUTHOR / 解像度: 16.2 Å / 解像度の算出法: FSC 0.5 CUT-OFF / ソフトウェア - 名称: SPIDER and GAP 詳細: Deposited map is composite of computationally-separated subunits and bound co-factors from the final map. 使用した粒子像数: 17672
最終 角度割当
詳細: SPIDER
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原子モデル構築 1
ソフトウェア
名称: URO
詳細
Protocol: Rigid body. Domains manually docked in O and refined in URO